One example of present tree processing units may be found described in Canadian Pat. No. 1,055,366 issued May 29, 1979 to Roger Sigouin. Such unit comprises a boom processing member, supported on a vehicle, which causes extension and retraction of a longitudinal boom having, at one end, tree gripping and debranching elements adapted to grasp a felled tree and to remove branches therefrom; second tree gripping elements are mounted to the member and are adapted to grasp the tree trunk adjacent its butt end so that debranching may be carried out by extending the boom as the first gripping elements loosely hold the tree. However, with such equipment, tree debranching is limited since, in most cases, the length of the cut tree is longer than the maximum length of the boom in the extended position. Hence, shear elements are provided at the front end of the boom to cut off the remaining un-delimbed portion of the tree, which portion is left to waste at the tree cutting site. It is noted that the number of un-delimbed tree portions represent a considerable loss of an important resource.